This program is directed at the Research and Development of a high energy density electrically rechargeable Nickel-Metal Hydride battery to serve as the internal power supply for Ventricular Assist Systems. To give the recipient of such systems maximum portability the internal battery pack should store enough energy for 45 minutes of operation. The battery pack should be as small and light weight as possible and have a life of five years. The metal Hydride system has the potential of being 50 % smaller than the Nickel-Cadmium system, the only other viable candidate to meet this application. The program is initially directed at the development of battery components best suited for this special application and then building cells to demonstrate and test the capabilities of this system. The ultimate goal is a battery that delivers greater than 44 Wh/Kg, 150 wh/1, has a life of five years 1825 cycles ( one cycle per day) and is compatible with implantable operation.